as far as I know there are no limitations. We used PADS 9.5 (netlist flow), our schematics were created using DxDesigner. Our preffered approach was Bottom-Up, which means we first created the schmatics of the block ("File" --> "New" --> "Schematic" [a new block appears in Project Navigator "Blocks"]) and then used the command "Tools" --> "Generate Block Symbol". This symbol was then added to our schematics from DxDatabook (Tab "Symbols", partition name: "[local symbols]").